Unbelief Its First Element. The sin of Adam consisted essentially, not in his bodily act, of course; but in his intentions. Papal theologians usually say that the first element of the sin of his heart was pride, as being awakened by the taunting reference of the Serpent to his dependence and subjection, and as being not unnatural in so exalted a being. The Protestants, with Turrettin, usually say it was unbelief; because pride could not be naturally suggested to the creature’s soul, unless unbelief had gone before to obliterate his recollection of his proper relations to an infinite God; because belief of the mind usually dictates feeling and action in the will; because the temptation seems first aimed (Gen. 3:1) to produce unbelief, through the creature’s heedlessness; and because the initial element of error must have been in the understanding, the will being hitherto holy.

The purpose of the crucifixion was to take this great reversal and reverse it. It is therefore important to look to Jesus, the author and finisher of our faith to understand more fully just what happened in the fall. Jesus is the exact image of the invisible God, and it is into Jesus' image that we are being conformed. Then what it was that is displayed in Christ's life and then the crucifixion encompasses all that man was meant to be, and all that happened to the image of God in which man was created.

While the mute creation downward bendTheir sight, and to their earthly mother tend,Man looks aloft, and with erected eyes,Beholds his own hereditary skies. (JC's Institutes )

Calvin gives us this as the image of man created, and here I use it in contrast. We get a pericope of this in the humiliation of Nebuchadnezzar. The pattern is set; when man makes himself the image of God, a reversal of roles, then God visits upon man the condecension and man becomes the image of his creation. Instead of looking up to the glory of God in whose image man was created, he assumes the posture of the lesser, on all fours; that pattern repeated until what remains is utterly comsumed by self-passion; man turns inward loving himself and committing acts of self love, homosexual, producing no life, receiving in himself the due penalty for sin.

Christ takes upon himself this image that man has created.

No reproduction of the reality ever captures the reality. Even this version has vain worth in transmitting it.

Behold, my servant shall act wisely; he shall be high and lifted up, and shall be exalted. As many were astonished at you— his appearance was so marred, beyond human semblance, and his form beyond that of the children of mankind— so shall he sprinkle many nations; kings shall shut their mouths because of him; for that which has not been told them they see, and that which they have not heard they understand.Isaiah 52:13-15

It is not so much what the fall did to man, as it is what it did to God. This is the great tragedy of the fall, that the glory of God was defaced, marred beyond recognition, and man in sinning was made into that image, an image that in the original was the perfection of perfections of righteousness. But now, that image is the perfection of perfections of evil.

I have not touched upon exactly what was marred, that is like trying to understand exactly what image and likeness mean. If you take the time to read or listen to the links, you will see that the image of God remains, but something has fundamentally changed and that change is systemic.